1. Field of the Invention
The present invention relates to a keypad for use in cellular phones, personal digital assistants, remote controls for various household electrical appliances, car remote controls, and a variety of keyboards, and also to a recycling technique thereof.
2. Description of the Related Art
Several types of cover members for push button switches are used for cellular phones, various remote controls, etc. One type of cover member is a keypad that is fabricated by integrally forming a key top portion that is the main body of the keypad and is capable of being pressed, and a base portion that elastically supports the key top portion so that the key top portion is movable in the direction that it is pressed. In this example, both portions are made of the same rubbery elastic body. Another type of cover member is a keypad that is produced by causing the key top portion of a resin key to adhere to the base portion of a rubbery elastic body. Still another type of cover member is a keypad that is formed by adhering the key top portion of a resin key to a resin film base portion. Of these, the keypad that is fabricated by integrally forming the key top portion and the base portion by use of a rubbery elastic body includes few composition materials and is economically produced, and thus the demand for use of the type is great, particularly in terms of easy assembling and achievement in thinning, in applications to personal digital assistants, cellular phones, remote controls, and keypads for desk-top calculators. Silicone rubber is primarily utilized as the materials for the keypad obtained by integrally connecting the key top portion and the base portion because of its desirable properties of cold resistance, heat resistance, weather resistance, precision moldability and electric insulation.
However, while silicone rubber has desirable properties, such as weather resistance, it cannot readily be recycled because it is a cross-linked polymer. The preservation of the global environment and the efficient utilization of resources have recently become increasingly valued, and so the difficulty in recycling does not match the needs of the time and presents an important, urgent, still-unsolved social issue.